The Foundation Trust Network believes its 200 members are spending around £30 million on freedom of information (FOI) requests a year, with administrative staff being pulled off normal duties to help reply to them.

At the moment public authorities like health trusts can only charge those making FOI requests if the cost of reply exceeds £450. The FTN wants this brought down, although it is not saying by how much.

Health campaigners have hit out at the move, describing it as "totally unacceptable" and "a terrible backwards step".

Ken Lownds, of the group Cure the NHS, set up in the wake of the nursing scandal at Mid Staffordshire NHS Foundation Trust, said: "It is already an absolute nightmare for patients or loved-ones to get information.

"This is designed to make it even more difficult. It is totally unacceptable."

Up to 1,200 mainly elderly people are thought to have died at hospitals in Stafford and Cannock Chase due to substandard nursing care between 2005 and 2008.

Peter Walsh, chief executive of the charity Action against Medical Accidents (AvMA), said FOIs were instrumantal in unearthing some of the problems there.

For example, Mid Staffs had "remarkably low" numbers of referrals to the General Medical Council and Nursing and Midwifery Council, he said, a fact only brought to light by FOIs.

He commented: "We think it would be a terrible backward step if the ability to obtain information under FOI was restricted."

Katherine Murphy, chief executive of the Patients Association, said: "This move could make it prohibitively expensive to obtain information through FOIs, which would not be in the interests of accountability of transparency."

It stated that while the FTN "supports the principles of openness and transparency", in the light of financial pressures "it would be sensible to re-focus FOI activity more clearly on matters of public interest and to streamline the process for responding to legitimate requests".

It estimated each trust was spending between £175,000 an £250,000 a year dealing with FOI requests, amounting to "significant sums of public money being diverted away from the core business of caring for patients".

Administrative staff were being diverted from jobs like appointment booking to deal with FOIs at some trusts, it noted.

Under the Act, public authorities including health organisations are required to respond to FOIs costing less than £450 without charging the requestor.

"This translates to 18 hours work, or two and a half person-days at £25 an hours before a charge is made for the cost of responding," according to the submission.

"The FTN believes that this threshold should be lowered."

The submission also noted that the average cost of dealing with a request was £500 - meaning any move to reduce the threshold could result in only the simplest being answered for free.

The FTN was also concerned that FOIs were being made for commercial reasons, with companies seeking to elicit information to help decide how to bid for services. Many came from media organisations, it added.

Last month the Ministry of Justice said there was "limited evidence" from requestors to the select committee's inquiry. However, the submissions deadline passed on February 3.

The select committee is due to review submissions later this year, before recommending changes to the law.